High-temperature elastic fluid turbine



A ril 20, 1948. D. J. BLOOMBERG HIGH TEMPERATURE ELASTIC FLUID TURBINEFiled Aug. 26, 1944 Fig.5.

Inventor: David J. Bloomberg,

His Attorne in o the atmosphere.

Patented Apr. '20, 1948 David J. Bloomberg, Newton, Mass, minor toGeneral Electric Company,

New York a corporation of Application August 26, 1944, Serial No.551,400

The present invention relates to high temperature elastic fluid turbinessuch as gas turbines for aircraft turbosuperchargers. Such turbines maybe operated at temperatures of the order of 1500 F. or higher whichmakes it necessary to provide cooling means, especially for the bearingand the bucket wheel. Also, where a single stage bucket wheel issupported on an overhung shaft and exhausts directly into atmosphere, itis important to reduce leakage of air into the clearance space betweenthe wheel and the nozzles for conducting gases thereto in order topreclude excessive temperatures within the wheel due to after-burning ofgases in the bucket passages.

The object of my invention is to provide an improved turbine which iseffectively cooled and in which the after-burning of combustiblematerial in the bucket passages due to air leaking into the clearancespace between the wheel and the nozzles is substantially reduced.

For a consideration of what I believe to be novel and my invention,attention is directed to the following description and the claimsappended thereto in connection with the accompanying drawing. I

In the drawing, Fig. 1 illustrates an exhaust gas operated turbine foraircraft turbosuperchargers; Fig. 2 is an enlarged view of part of Fig.l; and Fig. 3 is a view along line 3-3 of Fig. 2.

The turbine comprises a bucket wheel having a disk I and a plurality ofcircumferentially spaced buckets 2 attached to the rim of the disk. Thedisk I is secured, as by flash-welding to a shaft 3 supported on abearing 4. Operating gases are conducted to the passages formed betweenadjacent buckets by means of a nozzle box 5 which has an inlet 6 and aring of circumferentially spaced partitions I forming nozzle passagesbetween them for directing gases into the bucket passages of the wheel.The nozzle box has a waste conduit 8 through which some of the asessupplied to the box through the inlet conduit 6 may be wasted, that is,discharged directly The load output of the turbine may be controlled inknown manner by controlling the flow of gases through the waste conduit8. The nozzle box 5 is supported on a curved bafile 9 concentricallyspaced between the bearing 4 and the box and defining two annularchannels Ill and II therewith which serve to conduct cooling medium tothe turbine, as will be ex lained hereafter.

In order to cool the bucket wheel, cooling channels are formed onopposite sides of the disk I by means of two rotary shields, a shield l2disl 4 Claims. (CI. -41) posed on the outlet side of the disk and havingan inner edge secured to a hub portion of the disk by means of a weldIS. The outer edge of the rotary shield I2 is fused to a shroud l4formed at the base of the buckets by means of a weld IS. A similarrotary shield I6 is located on the inlet side of the disk and fused tothe hub portion of the disk by an annular weld l1 and to the shroud H byan annular weld l8, Fig. 2.

The buckets have base portions fused to the rim of the disk by welds l9.In addition to the shroud it formed at the base of each bucket tworadially spaced shrouds 20, 2| are formed at the tip of each bucket,together forming a channel or passageway 22. The buckets are hollow,each having a. radially extending channel 23 which extends through thetip of the bucket and near the base of the bucket is connected by twobranch channels 24, 25 with annular cooling spaces 26, 21 respectivelyformed between the wheel disk and the rotary shields l6 and I2respectively. The disk has a plurality of axial channels 28 connectingthe annular cooling spaces 28, 21.. Cooling air is conducted from thechannel l0 between the baiiie 9 and the bearing 4 throughcircumferentially spaced openings29 in the inner portion of the rotaryshield It Some of this cooling air in the space 26 flows ially outwardthrough the channels 24, 23 in the buckets. Another part of the coolingair flows through axial channels 28 in the disk and then radiallyoutward through the space 27 into the channels 25, 23, to be dischargedfrom the tips of the buckets.

In order to prevent cooling air in the annular channel Hi from leakinginto the clearance space between the buckets and the nozzles, means -areprovided to seal the nozzle box to the disk l6. This means comprises astationary sealing plate 30 fused at its outer edge to the wall of thenozzle box and having sealing engagement at its inner edge with adouble-deck labyrinth packing 31 having a portion or outer disk formingsealing engagement with a cylindrical extension 32 of the shield It toreduce leakage of air to the clearance space between the nozzle box andthe buckets. Said double-deck labyrinth packing is secured to the endcap oi. the bearing housing 4 and has another portion forming sealingengagement with the hub of the wheel to reduce leakage of air along theshaft 3 into the bearing housing I. The double-deck labyrinth packinghas a plurality of openings 33 establishing communication between thecooling channel in and the openings 29 in the rotary shield l6.

Somewhat similar sealing plate arrangements are disclosed inapplications Serial No. 594,628, filed May 19, 1945, now Patent No.2,414,841, in

the name of Dale D. Streid, and Serial No. 541,244,;

filed June 20, Auger.

Some of the air in the cooling channel In flows around the inner edge ofthe bailie 3 through the channel II to reduce heat transfer from thenozzle box to the bearing. In case of an aircraft the cooling air may beforced into the channel ill in known manner by means of a ram (notshown) facing the slipstream and the cooling air in the channel may bedischarged into the slipstream.

Gases discharged from the bucket wheel are directed into the atmosphereby means of an exhaust hood 34 which has an outer wall 35 with an edgeclosely spaced with the outer shrouds 2| of the buckets and an innerdished wall 36 with an edge portion closely spaced with the inner orbase shroud 4. The walls 35, 36 form a smooth annular discharge passagefor the bucket wheel, the wall 36 being supported on the wall 35 by aplurality of circumferentially spaced vanes 31. The exhaust hood alsoincludes a flanged collector ring 38 concentrically spaced from thebucket wheel and the wall 35 and secured to the nozzle box by aplurality of bolts 39. The ring 88 supports the wall 35 by means of aplurality of circumferentially spaced vanes 40 secured betweenconcentric portions of the ring 38 and the wall 35. An annular space 4|is thus formed between the bucket wheel and a portion of the wall 35 onone side, and the ring 38 on the other side for directing cooling airdischarged from the bucket tips into the atmosphere and to precludeleakage of air from the atmosphere into the turbine.

During operation, cooling air flows through the channel into the spaces26, 21, cooling both 1944, in the name of Claude H.

' sides of the wheel disk and from those spaces the cooling air flowsthrough the channels 24, 25, 23 of the buckets cooling the latter and tobe discharged from the tips of the buckets through the annular channel4| into the atmosphere. The space 22 formed between the radially spacedshrouds 20, 2| of the buckets has two important functions: first, itaids in balancing the pressures across the tips of the buckets, thusreducing leakage around said tips; and, second, it reduces the danger ofafter-burning of gases by air leaking into the exhaust hood 35. Thefluid passageway between the shrouds 20 and 2| should be designed for aminimum pressure drop and in some cases even a small amount of pumpingaction may be desirable in order to serve its purpose of keeping theleakage gas in the clearance space between the nozzle exit and thebucket entrance from flowing into the air space region. Some of thegases discharged from the nozzles towards the bucket wheels leakradially outward in the clearance space between the nozzles and thebucket These leakage gases flow in part passages. through the annularchannel 22, whence they are passed into the exhaust hood. In part suchleakage gases may flow into the annular channel or air space 4|, whencethey are discharged into the atmosphere. The major part of the gasleaking radially along the clearance space between nozzle and buckets,however, is diverted through the passageway 22 formed between the doubleshroud band into the exhaust gas passage inside the wall 34. The smallerpart of gas that leaks radially into the channel 4| inside the coolingring 38 is mixed therein with the cooling air discharged from thechannels 23 of the buckets and thereby cooled to a temperature below thecombustion point, thus precluding after-burning in the channel 4| in theproximity of the wheel. The mixture of gases discharged from the passage4| is at a suiiiciently low temperature .as to be non-luminous andnon-injurious to adjacent aircraft structure.

Having described the method of operation of my invention together withthe apparatus which I now consider to represent the best embodimentthereof, I wish to have it understood that the apparatus shown is onlyillustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

. 1. In a high .temperature axial flow gas turbine,

the combination of a rotor having a circumferential row of radiallyextending buckets secured thereto, radially spaced shroud meansassociated with each bucket near the tips thereof and forming an axialpassageway between each pair of adjacent buckets, a nozzle box includingnozzle means for conducting motive fluid to the buckets radially inwardfrom the shroud means, walls defining a turbine discharge conduit havingan edge forming a small clearance with the discharge side of the outershroud means,-and walls defining an annular cooling air passagesurrounding the outer shroud means, said axial passageways being locatedradially beyond the nozzle means and adjacent and in parallel flowrelation with the motive fluid path through the buckets, said nozzle boxhaving an annular wall portion forming small clearance spaces with theinlet side of the shrouds, whereby motive fluid leaking radially outwardfrom the nozzle means through said clearance spaces is caused to passthrough said axial passageways to substantially equalize the pressureacross the bucket tips and reduce mixing of the leakage fluid with thecooling air in said annular passage.

2. Gas turbine comprising a bucket wheel having a disk and a pluralityof circumferentlally spaced buckets attached thereto, a shaft secured tothe disk, a bearing for the shaft, a nozzle box concentricallysurrounding the bearing and having a ring of nozzles for conductingoperating gases to the buckets, means for cooling the bearing and thedisk including a cooling plate having inner and outer edges secured tothe disk and forming a cooling space therewith, and means forcirculating air through said space including channels formed in thebuckets, each bucket having an outer portion with. two radially spacedshrouds defining a passageway for gases leaking radially along theclearance space between the-buckets and the nozzles.

33. Gas turbine comprising a bucket wheel having a disk and a pluralityof circumferentially spaced buckets attached thereto, a shaft secured tothe disk, a bearing for the shaft, a nozzle box concentricallysurrounding the bearing and having a ring of nozzles for conductingoperating gases to the buckets, means for cooling the bearing and thedisk including a cooling plate having inner and outer portions securedto the disk and forming a cooling space therewith, means for circulatingair through said space including channels formed in the buckets, eachbucket having an outer portion with two radially spaced shrouds defininga passageway for gases leaking radially along the clearance spacebetween the buckets and the nozzles, and a ring concentricallysurrounding the bucket wheel for receiving coolcombustion point andafter-burning in proximity of the turbine is precluded.

4. Gas turbine for aircraft turbosuperchargers comprising a loucketwheel having a solid disk with axial channels therethrough, coolingplates on opposite sides of the disks rotatably secured thereto andforming cooling spaces therewith,

each bucket having a radial channel extending through its tip andcommunicating with said spaces, means for circulating cooling airthrough said spaces and channels, a nozzle box located on one side ofthe wheel and having a ring of nozzles for conducting gases to thebuckets, each bucket having a tip portion with two radially spacedcircumferentially extending shrouds forming an axial passageway, and anexhaust hood for discharging gases from the bucket wheel intoatmosphere, said hood having a wall with an edge forming a closeclearance with the outer shrouds, and means supporting said wallincluding a ring secured to the nozzle box and radially spaced from saidwall and the buckets forming an annular 6 mixing channel therewith forreceiving cooling air discharged from said spaces and gases leakingradially along the clearance space between the nozzles and the buckets,some of said leakage gases passing through said axial passageway intothe exhaust hood.

. DAVID J. BLOOMBERG.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 881,474 JudeMar. 10, 1908 986,317 Schmidt Mar. 7, 1911 1,061,648 Westinghouse May13, 1913 1,263,473 Schellens Apr. 23, 1918 1,640,784 Lorenzen Aug. 30,1927 1,819,864 Bloomlberg Aug. 18, 1931 FOREIGN PATENTS Number CountryDate 182,893 Great Britain July 10, 1922 504,214 Great Britain Apr. 21,1939 491,738

Germany Feb. 12, 1930

